Electrophotographic printing machine



P 24, 7 c. J. FITCH ELECTROPHOTOGRAPHIC PRINTING MACHINE 3 Sheets-Sheet1 Filed March 29, 1954 PIC-Ll INVENTOR. CLYDE J. FITCH Ji v.71

AT-roR NEY Sept. 24, 1957 c.- J. FITCH ELECTROPHOTOGRAPHIC PRINTINGMACHINE 3 Sheets-Sheet 2 Filed March 29, 1954 INVENTOR. CLYDE J. FITCH fI ATTORNEY Sept. 24, 1957 Filed March 29, 1954 c. J. FITCH 2,807,233

ELECTROPHOTOGRAPHIC PRINTING MACHINE 3 Sheets-Sheet 3 PI 6 5 INVENTOR.

CLYDE J. FITCH BY j JM JV.

ATTORNEY United States Patent 2,807,233 ELECTROPHOTOGRAPHIC PRINTINGMACHINE Clyde J. Fitch, Endicott, N. Y., assignor to InternationalBusiness Machines Corporation, New York, N. Y., a corporation of NewYork Application March 29, 1954, Serial No. 419,314 13 Claims. (Cl.118-637) This invention relates to electric printers in general, and tothe print transfer apparatus thereof in particular.

In keeping with electric printers in general, and withelectrophotographic printers in particular, the embodiment of thisinvention pertains to apparatus for elfecting a transfer of a visibleimage from an image carrying member, to a print receiving material, suchas a web of paper for example, and has for its purpose to provide animproved image, or print, transfer apparatus by which selective electricprinting may be effected.

To amplify the foregoing, the embodiment of this invention pertains toso'called xerographic machines capable of making a duplicate ofinformation appearing on source records, such as record cards forexample, on a print receiving strip by means of a transfer or printingprocess. As is well known to persons familiar with theelectrophotographic printing art, xerography is a term applied to aprinting process in which electrostatic latent images are renderedvisible by a suitable electrically charged toner powder, the resultingpowder image thereafter being transferred and fixed to a print receivingmaterial.

Another broad object of this invention is to provide a selectiveprinting electric printer whereby only selected information appearing ata certain place, or places, on a source record, is transferred from thesource record onto a copy record.

Another object of this invention is to provide an electrophotographicprinter having an improved image transfer apparatus associated therewithfor transferring by electric power only select electrically chargedpowder images. i

More specifically, another object of this invention is to provide axerographic printer having an image transfer'apparatus associatedtherewith which is capable of selectively effecting or disabling theimage transfer or printing process 9 In line with the foregoing, a stillanother object of this invention is to provide an electrophotographicprinter having an image transfer apparatus which requires lower voltagesthan used heretofore.

Other objects of the invention will be pointed out in the followingdescription and claims and illustrated in the accompanyingdrawingsywhich disclose, by way of example, the principle of theinvention and the best mode, which has been contemplated, of applyingthat principle.

In the drawings:

Fig. l is a somewhat diagrammatic view of an electrophotographic printerutilizing alshifting transfer roller apparatus at the image transferstation.

Fig. 2 is'a somewhat diagrammaticview of an electrophotographic printerutilizing an electric pulse controlled transfer apparatus at the imagetransfer station.

Fig. 3 is a flow diagram depicting generally the operations required inorder to place the image of source record information upon a printreceiving a copy record.

Fig. 4 is a somewhat diagrammatic view of the transfer apparatus andassociated mechanism taken along the plane 4-4 of Fig. l.

Fig. 5 is a somewhat diagrammatic view of the transfer apparatus andassociated mechanism taken along the plane 5-5 of Fig. 2.

Referring to Fig. 1, record cards 20 to be operated on are stacked inhopper 21, and are fed, one by one, by a conventional picker (not shown)of the type in Patent No. 2,448,830 issued to J. J. Robbins et al., eachcard cycle out of card hopper 21 to stacker 22. Successive pairs of feedrolls 23 and 24 cause cards 20 to be advanced during successive cardcycles past the optical projector apparatus 25.

Apparatus 25 includes a single light ray projector 26. which throws aconcentrated band of parallel light rays upon the constricted center ofthe aperture in member 27. Inasmuch as the reflecting surface of amirror 28 is over the aperture of member 27, the light band is caused toimpinge upon the surface of xerographic drum 29 when there are no cardspresent between member 27 and mirror 28.

As is shown in Fig. 3, each of the record cards 20 is shown to includeprinted information which is represented and identified by block 30. Dueto the fact that the surface of each card 20 has a light reflectingproperty," as the cards are fed past projector 25 (see also Fig. 1), andbetween member 27 and mirror 28, light rays are directed onto thesurface of drum 29 except when the symbols included within the printedinformation identified by the reference numeral 30, are not brought intoalignment with the aperture of member 27. It may be-seen then thatapparatus 25 includes a conventional light scanning means fortransferring the image of the aforesaid printed information onto thesurface of the xerographic drum 29.

The drum 29 is mountedon a shaft 31 which is suitably supported in framemembers (not shown) for rotation in a counterclockwise direction, saidshaft 31 being driven by an electric motor 34 (see also Fig. 4).Xerographic drum 29 includes an electrically conducting cylinder 35 anda printing element, or plate, 36 in the form of an electricallyinsulating or non-conducting image layer. This layer is carried by asheet of any flexible metal or other conductive material 37 that enablesits being flexed around and attached to the cylinder 35, the sheet 37being secured to the cylinder in any of the conventional ways ofattaching a printing plate to a supporting cylinder, as by means ofsuitable clamping devices. It is necessary, however, that the backingsheet 37 of the 7 image layer plate 36 is in good electrical contactwith thereon by-electrostatic charging,

the electrically grounded drum shaft 31. The electrically conductivebacking sheet 37 is preferably coated with a light sensitivephotoconductive insulating-material, such as plate 36, which may have apowder image produced exposure and powder development, after which thepowder image can be made into a permanent print image by transferringand fixing the developed powder image onto a print receiving materialsuch as paper strip, or web, 38.

With the feeding of record cards 20 from hopper 21 to stacker 22,xerographic drum 29 is caused to rotate at a speed which is correlatedto the record card feed speed, by means of drive shaft 31. As successiveincremental areas of the light sensitive photoconductive plate 36 aremoved past ion-producing unit 32, the aforesaid plate iselectrostatically charged by the ion-producing source. Carlson PatentNo. 2,588,699 may be referred to for a complete showing and descriptionof the afore-mentioned electrophotographic charging apparatus.

consequent upon the exposure of the surface of plate 36 to the image ofa record card 20, said image being caused by the light rays which aredirected from projector apparatus 25, those electrically chargedincremental areas of plate 36 onto which light rays are directed, aredischarged, and those areas not illuminated by light rays remaincharged. This, of course, is for the reason that plate 36 is aphotoconductive insulating material which is in electrical contact withconductive backing sheet 37, said sheet 37 being electrically connectedto grounded shaft 31. Hence, after photoconductive plate 36 is exposedto the light image of a record card, an electrostatic latent image ofthe record card will remain on plate 36, this electrostatic latent imagebeing one wherein the dark characters within printed information imageareas identified by reference numeral 30 (Fig. 3) cause chargedcharacters within image areas identified by reference numeral 30a whichcorrespond to the afore-mentioned dark characters, and wherein the lightimage areas corresponding to the record card surface are no longercharged.

Continued rotation of the xerographic drum in a counterclockwisedirection causes the image portions 30a of plate 36 (Fig. 3) to be movedinto developing chamber 39. A similar chamber is utilized in theapparatus of Schatfert Patent No. 2,576,047. The electrically chargedtoner powder in chamber 39 will flow onto plate 36 and over theelectrostatic latent image, and will move downwardly thereover due togravity in a continuous stream, thus being evenly distributed over theimage layer. The surplus toner powder which does not adhere to theelectrostatic latent image formed on plate 36, falls into a receivingreceptacle within chamber 39 so as to cause the powder to be completelyretained within the chamber housing. The powder image that is formed onthe image plate 36 visibly defines the electrostatic latent image, i.e., the powder will cling only to the dark printed information imageareas having an electric charge there- The powder in chamber 39 may be afinely powdered dye, pigment, carbon or other black or coloredsubstance, or in some cases a white powder such as zinc oxide. Asuitable electroscopic developer powder, or toner, is described inCopley Patent No. 2,659,670

Continued rotation of drum 29 causes the powder image on plate 36 tomove out of chamber 39 and into the transfer, or printing, stationhaving transfer roller 40 thereat. The transfer roller comprises aninner-metallic portion 41 and an outer portion 42 of very resilient oryielding material having a high electrical resistance, as for example, alayer of soft semi-conducting rubber. The transfer roller requires aresilient outer portion so as to compensate for mechanicalirregularities of the xerographic drum surface, and to preventmechanical damage to the photoconductive surface thereof. The conductiverubber is preferably a very poor conductor of electricity, and may havean electrical resistivity of approximately ohms per cubic centimeter.The resistance value is not too critical and it may be greater than theaforementioned value. However, the resistance value is preferably notless than 10 ohms per cubic centimeter.

Transfer roller 40 is biased by springs 43 (see also Fig. 4) in thedirection of photoconductive plate 36 so that web 38 is sandwichedtherebetween. The transfer roller is supported by the shaft is journaledin arms 45. The latter arms are each at- 44 thereof which, in turn,

tached to cam follower arms 46 which are also fixed to shaft 47 whereoncam follower roller 48 is mounted. Web feed control arms 49 having feedroller 50 attached thereto are also fixed to shaft 47 so that arms 45,46 and 49 act in unison. The afore-mentioned arms are pivotally mountedupon shaft 54, the said shaft having idler roller rotatably mountedthereon, and being fixed in printing machine support frames, such asframe 53 for example. As is shown in Fig. 1, web 38 is fed from reel 56past drag rollers 57, around idler roller 55 and transfer roller 40,between fixing rollers 58, feed rollers 50 and 59, and rollers 60, toreel 61.

In order to produce a permanent image, it is necessary to fix onto theprint receiving material, such as web 38 for example, those powderimages that are transferred thereto. One means for fixing powder imagesutilizes a line pressure such as is afforded by the pressure fixingrolls 58 (Fig. 1) and 158 ('Fig. 2). A sufficient line pressure forexample 500 pounds per lineal inch of contact, will cause the tonerpowder to flow into the fibers of the web material. An oil pad 68(Fig. 1) and 168 (Fig. 2) is provided to remove any excess powder whichwill cling to the upper fixing roller.

As long as powder images are plate 36 onto web 38,

to be transferred from the generally T-shaped unit comprised of arms 45,46 and 49, will be positioned under the urging of springs 43 so thattransfer roller 40 causes Web 38 to engage plate 36. In addition, thisgenerally T-shaped unit is positioned so that roller 50 maintains theweb in contact with continuously rotating drive roller 59 in order tocause the web to advance. It is necessary to point out that roller 59 isspring-biased in an upward direction so that there is assurance of goodcontact between transfer roller 40 and drum 29 during the periods thatrollers 50 and 59 are in contact. In order to disable printing, i. e.,to prevent the transfer of charged powder images, cam 62 is rotated soas to engage roller 48 which, in turn, causes arms 45, 46 and 49 topivot in a. counterclockwise direction. Hence, transfer roller 40 willbe moved away from drum 29, and web feed roller 50 will be moved awayfrom drive roller 59, to thereby disable the friction-drive applied toweb 38 by rollers 50 and 59. In addition, transfer roller 40 is moved asufficient distance to carry the web into engagement with braking member65 whereby web 38 is stopped immediately by the braking action.

In order to remove any toner powder which remains on the surface ofplate 36 prior to the incremental areas thereof becoming charged againby ion-source unit 32, a rotating plush roller 66 is provided. Thisroller is po sitioned within a housing 67 for retaining the powderremoved by the counterclockwise rotating action of the roller, from thexerographic drum plate 36.

A comparison of the electrophotographic printers shown in Figs. 1 and 2will reveal a similarity between many elements thereof. Hence, forpurposes of clarity and simplicity, those elements in the printer ofFig. 2 which are similar to corresponding elements in the printer shownin Fig. 1, will be identified by a series reference numeralcorresponding to the reference numeral used in Fig. 1. That is, forexample, the xerograph'ic drum of the printer shown in Fig. l, isidentified by the reference numeral 29, and the xerographic drum of theprinter shown in Fig. 2 is identified by the reference numeral 129.

Referring to Fig. 2, record cards to be operated on are stacked inhopper 121, and are fed, one by one, each card cycle out of card hopper121 to stacker 122. Successive pairs of feed rolls 123 and 124 cause therecord cards to be advanced during successive card cycles past theoptical projector apparatus 125.

Apparatus 125 includes a single light ray projector 126 for directing aband of light rays upon the constricted center of the aperture in member127, to thereby effect a conventional light scanning operation wherebythe image of the printed information on the record card is trans- 75ferred to the surface of the xerographic drum 129.

Xerographic drum 129 is mounted on a shaft 131 which is driven by anelectric motor 134 (see also Fig. in a counterclockwise direction. Theaforesaid drum includes an electrically conducting cylinder 135 and alight sensitive photoconductive insulating printing plate 136. Thisplate is carried by a sheet of any flexible metal or other conductivematerial 137 that enables its being flexed around and attached to thecylinder 135.

With the feeding of record cards from hopper 121 to stacker 122, thexerographic drum is caused to rotate by shaft 31 at a speed which iscorrelated to the record card feed speed. As successive incrementalareas of the light sensitive photoconductive plate 136 are moved pastcharging roller 170, the aforesaid plate is caused to have an electricalcharge placed thereon. The charging roller includes an inner-metallicportion 171 and an outer portion 172 of very resilient or yieldingmaterial having a high electrical resistance, as for example, a layer ofsoft conducting rubber. Inasmuch as this charging roller issubstantially similar to the upper cylindrical member or roll used inthe electrical printing apparatus described in Hooper Patent No.2,520,504, reference may be had to this patent for more detailedinformation.

Consequent upon the exposure of the surface of plate 136 to the image ofa record card 120, an electrostatic latent image is caused to remainthereon in the manner, and for the reasons, mentioned hereinbefore.Continued rotation of the xerographic drum 129 in a counterclockwisedirection causes the electrostatic latent image-exposed portions ofplate 136 to be moved into developing chamber 139 wherein theelectrically charged toner powder is permitted to flow onto plate 136and over the electrostatic latent image. As a result thereof, a powderimage which visibly defines the electrostatic latent image is formed onthe surface of plate 136. Further rotation of the ,xerographic drumcauses the powder image on plate 136 tomove out of chamber 139 and intothe transfer, or printing, station having transfer cylinder 175 thereat.

Transfer cylinder 175 includes end wheels 176 (see also Fig. 5) and 177,and a conductive roller 178. The diameter of roller 178 is smaller thanthe diameters of end wheels 176 and 177 by an amount such that a gap ofapproximately 0.002 inches exists between plate 136 and web 138. Inorder that the web does not rub against the drum surface during printsuppress time, it is necessary that the diameter of roller 178 issmaller than the diameter of the end wheels by an amount greater thantwice the thickness of the web. Roller 178 is rotatably mounted oncylinder shaft 179 in order that feeding of web 138 may be stoppedduring non-print periods even though the Xerographic drum is caused tocontinue rotating. The wheels 176 and 177 are journaled and arranged insuch a manner as to be electrically separated from shaft 179 which, asshown in Fig. 2, is used to supply electric power to conductive roller178, and the cylinder shaft is biased in a direction towards drum 129 byconventional means so that the end wheels ride on the peripheral surfaceof the drum. As is shown, web 138 is fed from reel 156 past drag rollers157, around rollers 160 and 178, between fixing rollers 158, feedrollers 150 and 159, to reel 161. In order to remove any toner powderwhich remains on the surface of plate 136, prior to the incrementalareas thereof becoming charged again by charging cylinder 170, there isprovided a rotating plush roller 166. This roller is positioned within ahousing 167 for retaining the powder removed by the counterclockwiserotating action of. the roller, from the xerographic drum plate 136.

Image transfer apparatus Referring to Fig. 1, transfer roller 40 isconnected to a source of positive potential, e. g., 1000 volts, via wire70 and manually operated switch 71 and/ or cam contacts C1. Theinsulating image plate 36, carried by the conductive supporting plate37, is charged negatively, whereas the toner powder which produces theimage by adherence to the plate 36, is charged positively bytriboelectric action of the carrier material to which the electroscopicpowder particles adhere until separated therefrom by the strongerattractive force of the negatively charged insulating image plate 36.Inasmuch as backing sheet 37 is electrically connected to grounded shaft31, an effective condenser is obtained at the transfer station whereinbacking sheet 37 and transfer roller 40 serve as plates thereof, andinsulating plate 36 along with web 38 act as the dielectric thereof. Theaforementioned positive potential applied to transfer roller 40 issulficient to cause an electric field to exist between the transferroller 40 to backing plate 37. This electrostatic field or potentialgradient causes the powder adhering to plate 36 to transfer onto web 38,Whereafter the transferred powder on web 38 is fixed thereto by pressurerollers 58. In order to disable printing, i. e., to prevent the transferof charged powder images, cam 62 is rotated so as to engage cam followerroller 48 which, in turn, causes arms 45, 46 and 49 to pivot in acounterclockwise direction. This, as stated previously, causes transferroller 40 to be moved away from xerographic drum 29, and web feed roller50 to be moved away from drive roller 59. The resulting air spacedefined by the outer peripheries of plate 36 and transfer roller 40 issufiicient to preclude a transfer of the powder from xerographic drum 29onto web 38. Inasmuch as the generally upward movement of roller 50disables the friction-drive that is applied to web 38 by rollers 50 and59, and since the shifting of transfer roller 40 is of such a nature asto brake web 38 by means of braking member 65, web 38 is stoppedimmediately.

Referring to Fig. 2, a suitable positive potential, e. g., +2000 volts,is applied to the conductive roller 178 of transfer cylinder 175 vialine 177. Hence, roller 178 is electrified so that a resultingion-stream transfers the toner powder adhering to plate 136 onto web138, and the transfer of power is effective so long as cam contacts C2.are closed. In order to disable the printing operation, i. e., thetransfer of powder images, cam contacts C2 are caused to open.Concurrently therewith, web feed drive roller 159 is stopped so as tostop the feeding of web 138. The drag load applied to web 138 by rollers157, 158, 160, and 159, is sutficient to prevent any creep thereof.Inasmuch as roller 178 (see also Fig. 5) has a diameter which is smallerthan that of end wheels 176 and 177, cylinder need not be shifted awayfrom xerographic drum 129 during the periods when web 138 is not beingmoved.

It is necessary to point out at this time that the description thus farpertains to a positive-to-positive printer. However, a reverse imageprinter may be had simply by employing a reversal developer powder sothat the charge on the powder image is reversed, and by connecting thetransfer roller or cylinder to a voltage that is negative with respectto the Xerographic drum. A suitable voltage may range from negative 1000volts to negative 2000 volts.

In order to avoid undue complexity and prolixity, a positive-to-positiveprinter will be described for illustrative purposes only. This is not tobe construed as a limitation, however, but is to be accepted as apreferred embodiment.

Operation The printed information which is to be transferred to theprint receiving web is identified in the illustrated embodiments byreference numeral 30 (Fig. 3) and is typed, for instance, onthe sourcerecords. The information to be transferred need not be in reversed orderon the source records because the double reversal effected by theprojection of the image onto plate 36 (Fig. 1), for example, and thesubsequent transfer of the powdered image onto web 38, causes theinformation transferred to the web to be arranged in the same order asis the information on the source records.

Referring to Figs. 1 and 4, xerographic drum 29 is shown to be operatedby motor 34 through a speed reduction unit 80 having gears, or the like,therein, and which is also connected to drive unit 81 so as to cause cam62 and cam contacts CI to operate in step with the drum. The rotationalspeed of drum 2% and cam 62 is so correlated that whenever theimage-portion 30a of the card provided with the information to betransferred, is disposed between drum 29 and transfer roller 40, cam 62is in a position whereat springs 43 are free to move web 33 intosimultaneous contact with plate 36 and transfer roller 40. As mentionedhereinbefore, the information is thereby transferred from thexerographic drum to the paper strip 38. A further movement of thexerographic drum and cam 62 will cause transfer roller 49 to be shiftedfrom an effective print position to a non-print position only after thedesired information 3001 has been transferred to web 38. The transferroller will remain in the latter non-print position until a succeedingimage 300 is moved into the transfer station. Inasmuch as feed roller 50is moved away from drive roller 59 during nonprint time, web 38 is notadvanced during this time.

It is apparent that cam 62 may be adjustable, or interchangeable withanother cam so that the height of the information to be transferred tothe web can be varied according to a predetermined requirement. It isapparent too that cam 62. may be provided with a number of cams, and inthis event, a number of horizontal strips can be transferred to the webfrom several card sections. In addition, the length of transfer roller40 can be varied so as to be effective to transfer to web 38 onlypredetermined information. The arrangement may be such, for example,that the length of roller 4% corresponds to the vertical width of theinformation on the card. Furthermore, roller 49 may be laterallyadjustable so that the same presses onto xerographic drum 2 9 only whena certain part of the powder image is moved into the transfer station.Transfer roller 4'0 may also be subdivided so that a number of verticalportions are printed from a single card section. Thus, by the abovearrangements any printed information from a source record can betransferred to a print receiving material by merely varying the twotransfer control members; namely the cam 62 and the transfer roller 40.

As stated previously, printing at the transfer station may be disabledby simply shifting transfer roller 40 away from xerographic drum 29.However, in some cases it may also be desirable to disrupt the powerapplied to transfer roller 46 whenever the transfer roller is shiftedaway from the xerographic drum. This type of operation may be had byopening manually operated switch 71 and permitting the electric powerthat is applied to transfer roller 40 to be under control of camcontacts C1. The cam contacts may be timed so that a circuit iscompleted to roller whenever the said roller is shifted to a printingposition, and opened whenever roller 40 is shifted to a non-printingposition.

Referring to Figs. 2 and 5, Xerographic drum 129 is operated by motor134 through a suitable gear unit 180 which is also connected to a drivenunit 181 for operating paper feed roller 159 and cam contacts C2. Unit181 includes a gear sector for operating roller 159 intermittently sothat roller 159 is operated to advance web 138 whenever the image lfitlato be transferred is moved to the printing, or transfer, station. Camcontacts C2 are timed to be in step with the movement of feed roller159; i. e., the contacts are closed so as to apply a positive potentialto conductive roller 178 during the time that image 130a is at thetransfer station, and open during all other periods. As describedpreviously, the diameter of roller 173 is smaller than that of endwheels 176 and 177 and, as a result thereof, web 138 may be stoppedduring non-print time even though Xerographic drum 12f continues torotate. That is, there is a sufficient clearance between the outersurface of web 138 and the outer surface of plate 136 so that either theweb or the plate may be stopped during a movement of the other Withoutcreating a rubbing action therebetween.

In summation, apparatus have been shown and described whereby selectiveelectrophotographic printing is effected in order to transfer onto aprint receiving material only select information in a predeterminedplace, or places, of a source record. And while there have been shownand described and pointed out the fundamental novel features of theinvention as applied to preferred embodiments, it will be understoodthat various omissions and substitutions and changes in the form anddetails of the devices illustrated and in their operation may be made bythose skilled in the art, without departing from the spirit of theinvention. It is the intention, therefore, to be limited only asindicated by the scope of the following claims.

What is claimed is:

1. In an electric printer comprising a rotatable printing drum having aninner electrically conducting member and an outer dielectric surfaceportion adapted to support transferable images thereon for transfer at aprinting zone to a Web, a conductive cylinder for supporting the web ina position at the printing zone intermediate said printing drum and saidcylinder, a source of electric power, electric circuit means forconnecting said conducting member and said cylinder to said powersource, means for rotating said printing drum, means for moving said webat a lineal speed correlated to the peripheral speed of said printingdrum, and circuit interrupter means operable synchronously with saiddrum rotating means for governing said electric circuit means so thatelectric power is applied to said member and said cylinder as saidtransferable images are moved through the printing zone, to therebyeffect a transfer of said images from said printing drum to said web.

2. In an electrophotographic printer comprising a printing member,shiftable means normally at: one limit of movement nearest said printingmember for applying an electric force at a printing zone, means formoving said printing member relative to said electric force applyingmeans, means for feeding a print receiving material between said memberand said electric force applying means in a timed relation to themovement of said member, and means operable synchronously with saidprinting member moving means for shifting said electric force applyingmeans from said one limit whereat said electric force applying means iseffective to cause printing, to another limit of movement away from saidprinting member whereat said electric force applying means isineffective to cause printing.

3. In a printer of the class described having a printing member, meansincluding a shiftable conductive cylinder for producing a printeffecting electric force at a printing Zone, means for moving saidprinting member relative to said cylinder in a direction substantiallyparallel to the axis of said cylinder, means for feeding a printreceiving material between said member and said cylinder in a timedrelation to the movement of said member, and means operablesynchronously with said member moving means for normally maintainingsaid conductive cylinder in pressure engagement with said web and saidprinting member and for shifting said conductive cylinder away from,said printing member to thereby effect selective printing at theprinting zone.

4. In a printer according to claim 3, means operable synchronously withsaid cylinder shifting means to control said print receiving materialfeeding means so that said material is advanced only when said cylinderis maintained in pressure engagement with said web and said printingmember.

5. In an electrophotographic printer having a rotatable printing drumincluding an inner electrically conducting member and an outerdielectric surface portion adapted to support electrically chargedpowder images thereon for transfer to a web, a shiftable conductivecylinder for supporting the web between opposing surfaces of saidcylinder and said drum, a source of electric energy, electric circuitmeans for connecting said conducting member and said cylinder to saidsource, means for continuously rotating said drum, whereby said web isfed in a path adjacent to a portion of the periphery of said drum and ata lineal speed correlated to the peripheral speed of said drum, astationary web braking member, and means operable synchronously withsaid drum rotating means for shifting said cylinder from a printingposition whereat said web engages said drum and said cylindersimultaneously, to a non-printing position whereat said web engages saidbraking member and said cylinder.

6. In an electrophotographic printer, the combination of apparatus at aprinting zone for transferring electrically charged powder images to aweb comprising an electrostatically charged printing drum adapted tosupport said charged powder images thereon, radially shiftable means fornormally supporting said web in contact with said printing drum at onelimit of movement of said shiftable means and out of contact with saiddrum at the other limit of movement thereof, said web supporting meansincluding a rotatable cylinder having a surface layer of conductingresilient material for producing by electric current an electrostaticfield of force at the region of contact of said web and said printingdrum, said lines of force thereof acting in a direction to transfer saidcharged powder images from said drum to said web, means for rotatingsaid printing drum whereby said web is normally moved at a lineal speedcorrelated to the peripheral speed of said drum, and means for shiftingsaid web supporting means radially with respect to the axis of said drumfrom said one limit of movement to said other limit of movement so thatthe strength of said electrostatic field of force at the printing zoneis changed respectively from one effective to cause printing onto saidweb moving with said drum and to one non-effective to cause printingonto said web now stationary and supported only by said cylinder.

7. The combination in an electric printer having a printing drum adaptedto support successively arranged transferable information thereon, ofdrive means for rotating said drum at a speed correlated to the linealspeed of a paper strip, a shiftable conductive cylinder at a printingzone for supporting said paper strip between opposing surfaces of saidcylinder and said drum, a power source, electrical circuit meansconnecting said power source to said cylinder and said drum, and a camdevice operable synchronously with the drum drive means for shiftingsaid cylinder relative said drum in one direction so as to produce anelectric force at the printing zone to effect printing only wheneversaid transferable information is moved through the printing zone, and inanother direction so as to stop movement of said paper strip onlywhenever said transferable information is outside the printing zone.

8. In a printer of the class described having a printing member, meansincluding a conductive cylinder having a resistivity of at least ohmsper cubic centimeter for producing an electric force at a printing zone,means for moving said printing member relative to said cylinder in adirection substantially parallel to the axis of said cylinder, means forfeeding a print receiving material between opposing surfaces of saidmember and said cylinder in a timed relation to the surface movement ofsaid member, and means operable synchronously with said member movingmeans for shifting said conductive cylinder towards and away from saidprinting member to thereby control printing at the printing zone.

9. The combination in an electric printer having a rotatable printingdrum adapted to support successively arranged items of transferableinformation thereon, of drive means for rotating said printing drum at aspeed correlated to the lineal speed of a paper strip, a conductivecylinder having a resistivity of at least 10.ohms per cubic centimeterpositioned at a printing zone for supporting the paper strip betweensaid cylinder and said drum, and

wards said drum so as to produce an electric force'at the printing zoneto effect printing whenever each one of said items oftransferableinformation is moved through the printing zone and in a direction awayfrom said drum so as to stop movement of said paper strip whenever saiditems of information are outside of said printing zone.

10. An electrophotographic printer transfer station comprising aphotoconductive member adapted to support charged powder images thereon,an electrically conducting transfer roller, means for feeding a powderreceiving web between opposing surfaces of said photoconductive memberand said transfer roller, yielding means urging said photoconductivemember and said transfer roller into engagement, and means associatedwith said web feeding means to cause said yielding means to be out ofengagement with said member when the advancing movement of said Web isstopped.

11. Apparatus for transferring select ones of a plurality ofelectrically charged powder images to the surface of a sheet material,comprising a printing member adapted to support a plurality of saidcharged powder images arranged successively thereon, means including aconductive rotatable cylinder for applying an electric force at aprinting zone, means for normally feeding said sheet material throughsaid printing zone defined by the opposing surfaces of said printingmember and said conductive cylinder so that said cylinder is rotatedthereby, drive means for moving said printing member in a directionsubstantially parallel to the axis of said conductive cyl inder and in atimed relation to the feeding movement of said sheet material, means forcontrolling said electric field of force from one limit whereby saidcharged powder images may be transferred from said printing member tosaid sheet material, to another limit whereat said charged powder imagesmay not be transferred from said printing member to said sheet material,and means effective concurrently and conjointly with said electric forceapplying means to render said sheet material feeding means disabled whenthe strength of the electric field of force is altered to said anotherlimit.

12. In a machine of the class described, a printing member, meansincluding .a conductive cylinder for applying an electric force at aprinting zone, means for moving said printing member relative to saidcylinder in a direction substantially parallel to the axis of saidcylinder, means for feeding a print receiving material through saidprinting zone defined by opposing surfaces of said member and saidcylinder in a timed relation to the movement of said member, meansoperable simultaneously with said member moving means for controllingsaid electric force applying means so that the electric force at saidprinting zone is effective for printing, and means including saidcylinder for preventing feeding of said print receiving material whenthe electric force at said printing zone is ineifective for printing.

13. In a printing machine of the class described having a printing drum,a web feeding roller, and means for continuously rotating said drum andsaid roller; a transfer apparatus comprising a web idler roller; aconductive cylinder; a pivotally mounted member adapted to support saidweb idler roller and said conductive cylinder; a stationary web brakingelement; resilient means (a) for normally maintaining said web idlerroller in a web feeding position relative said web feeding rollerwhereby said web is in pressure contact with both of said rollers sothat said web is advanced through a printing zone defined by theopposing surfaces of said printing drum and said cylinder, and through aweb braking zone defined by the opposing surfaces of said cylinder andsaid stationary braking element, and (b) for normally maintaining saidcylinder in a print efiecting position relative said printing drumwhereby said web is in pressure contact with said printing drum and saidcylinder; and means for pivoting said pivotally mounted member so thatsaid web idler roller is moved relative said web feeding roller and outof the web feeding position, and said cylinder is moved concurrentlytherewith relative said printing drum and out of the print effectingposition to a web braking position relative said braking element wherebysaid web is in pressure contact With said cylinder and said stationaryl0 braking element so that said Web is stopped.

UNITED STATES PATENTS Schwarzschild Nov. 29, 1898 Vannote June 19, 1928Carlson Sept. 12, 1944 Walkup et a1. Nov. 6, 1951 Carlson Jan. 6, 1953Pethick Apr. 7, 1953 Butterfield et a1. June 16, 1953

